Crawler cranes Crawler cranes

This includes reducing the ground
bearing pressure by spreading the
outrigger pad load over a wider
area with a suitable mat. As well as
using cribbing to provide a level
base for the mat on sloping or
stepped ground. It is at this stage
that a good deal of skill comes in to
the equation. The operator however
should have been trained on how to
do this properly and be equipped
with the materials to handle most
ordinary ground conditions.
If you have rented in the crane,
even on a contract lift, you as the
customer are still responsible for
determining the ground conditions
on site and to inform the crane
company if there are any underground
voids. If any doubt exists
the operator must be told.
Test the ground
On most everyday lifts the operator
can test the ground, by raising the
load a few mm off the ground with
the boom directly over each outrigger.
The operator of a big truck mounted
lift can do the same with a couple
of people or a load in the basket.
This is usually a very simple thing
to do and well worth it, if only for
piece of mind.
Some operators still forget to set
their outriggers first.
With the largest cranes, and lifts,
this quick and dirty method is not
the way to go, some form of ground
survey needs to have been done so
the contractor and crane company
know exactly what to expect.
The other rule of course is - if in
doubt use bigger mats.
When working on slopes with a self
drive machine, it is best to use a
machine that has been designed for
such work such as a spider lift.
They usually feature larger built-in
pads that have sufficient articulation
to adjust to the contour of the
slope, avoiding the need to level
the slope with cribbing. Care
needs to be taken though that
the machine cannot slip down
the slope once in the air.
What Mats?
It was not so long ago that second
hand railway sleepers and timber
off cuts were the order of the day
when it came to outrigger mats,
with little consideration to their
A good quality
wood mat
used with a
self erecting
tower crane
suitability. The problem with such
material is that some timber will split
easily when under load. While the
use of a number of lengths of wood,
requires a level of expertise to set
up safely, so that it does not move
or kick out from under the outrigger
jack. Differing timber thicknesses
complicates the task still further.
Modern nylon, or better still,
polyethylene mats are clean and easy
to use and handle with built in grips
or lifting points. The best are almost
indestructible and will flex slightly
to profile the ground, and then
return to their original shape, time
after time. Standard mats are ideal
for most aerial lifts, telehandlers,
loader cranes and mobile cranes up
to around 125 tonnes. Thus covering
most routine applications.
A large volume of Eve
trakway was used at
the Don Valley Rolling
Stones concert to
protect the grass and
provide access for
cranes
c&a
Don't pinch the pennies
When sourcing this type of mat
it is well worth spending a little
more for a good quality product.
Given that they appear to be
made of the same material, there
is a tendency to buy on price
alone. The best producers provide
long guaranties with a no quibble
‘break it and we'll replace it’
policy. Cheap mats will bend
crack and delaminate. When
deciding on material, in general
terms, polythene is too flexible,
nylon is more likely to crack but
polyethylene is just right, as
Goldilocks said.
Customised & branding
An increasing number of suppliers
now offer a wide range of square,
rectangular or round mats off the
shelf and available for immediate
delivery. They can also be made
to order, to suit a particular job,
machine or customer. Some suppliers
will customise them to your precise
specification, in terms of colour,
company name or logo and surface
finish. A number of company's offer
a textured surface on the mat to
help prevent slippage, while this
is not a bad idea, don't pay a
premium for it, as after only a few
uses even the smoothest pad will
have become textured from use.
For larger cranes large steel mats,
often made from I-beams welded
together, are still very popular,
and of course very rigid and
predictable. Polyethylene mats are
now available in larger sizes with
thicknesses of 160mm making
them practical for cranes as
large as 400 tonnes or more. The
benefit of course is that they are
lighter to transport and are usually
less expensive. For big applications
though, properly selected and
engineered wood mats are still
highly popular and offer a high
degree of versatility. And if from
managed forests are also
environmentally friendly.
outrigger mats
Good quality wood mats are ideal as a base for crawler cranes
Tracks and
ground protection
When ground conditions are very
soft, large mats or track way may
be needed, to get the equipment in
to the lift area and then to provide a
foundation for the crane. This is as
true for crawler cranes as it is for
mobiles and big truck mounted lifts.
For pure site access needs, the best
choice is usually aluminium track
way, pioneered by Eve and rented
out on an installed basis. An
alternative that is growing in popularity
is polythene/polyethylene modular
track pads. These are large
rectangular mats that can be linked
together to produce a temporary
roadway. Not only can they be used
to take a wheeled machine across
very soft ground, but also used to
protect delicate surfaces such as
lawns, or decorative paving. In a
recent example, two by four metre
polyethylene mats were used to
allow an 80 tonne crawler crane to
walk across a marble floor, with
ground bearing pressures of less
than 2.5 tonnes/sq metre.
In North America many rental
companies stock such track pads
for rent along with the machine.
Well planned storage for shoring
timbers on a Liebherr AT crane
October 2006 cranes & access
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